Web開發使用 Controller 基本上可以完成大部分需求，但是我們還可能會用到 Servlet、 Filter、Listener等等
二.在spring boot中的三種實現方式
方法一：通過註冊ServletRegistrationBean、 FilterRegistrationBean 和 ServletListenerRegistrationBean 獲得控制
/**
* 自定義servlet
*
* @author wujing
*/
public class CustomServlet extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("servlet get method");
doPost(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("servlet post method");
response.getWriter().write("hello world");
}
}
/**
* 自定義filter
*
* @author wujing
*/
public class CustomFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println("init filter");
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
System.out.println("do filter");
chain.doFilter(request, response);
}
@Override
public void destroy() {
System.out.println("destroy filter");
}
}
/**
* 自定義listener
*
* @author wujing
*/
public class CustomListener implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent sce) {
System.out.println("contextInitialized");
}
@Override
public void contextDestroyed(ServletContextEvent sce) {
System.out.println("contextDestroyed");
}
}
註冊bean
@Bean
public ServletRegistrationBean servletRegistrationBean() {
return new ServletRegistrationBean(new CustomServlet(), "/roncoo");
}
@Bean
public FilterRegistrationBean filterRegistrationBean() {
return new FilterRegistrationBean(new CustomFilter(), servletRegistrationBean());
}
@Bean
public ServletListenerRegistrationBean<CustomListener> servletListenerRegistrationBean() {
return new ServletListenerRegistrationBean<CustomListener>(new CustomListener());
}
方法二：通過實現 ServletContextInitializer 接口直接註冊
implements ServletContextInitializer {
@Override
public void onStartup(ServletContext servletContext) throws ServletException {
servletContext.addServlet("customServlet", newCustomServlet()).addMapping("/roncoo");
servletContext.addFilter("customFilter", new CustomFilter())
.addMappingForServletNames(EnumSet.of(DispatcherType.REQUEST), true,"customServlet");
servletContext.addListener(new CustomListener());
}
方法三：在 SpringBootApplication 上使用@ServletComponentScan 註解後，直接通過@WebServlet、@WebFilter、@WebListener 註解自動註冊